Generally speaking, the tubes are mounted in the perforated plates and are then fixed thereto by expanding or by welding at the power station size. This operation takes a long time since there are many tubes to be put into place.
Work has thus been done to provide modular bundles of tubes which are factory-built so as to minimize the number of operations that need to be performed on site, and hence to reduce the time spent on site.
FIGS. 1 and 2 thus show an example of a known arrangement used at the San Onofre power station in California, USA. The steam condenser comprises a bundle of tubes 1 between perforated plates 2 and 3 which is constructed in a factory and then assembled, on site, with the body of the condenser 4.
The bundle of tubes comprises four modules which are assembled together on site. Before the modules arrive, the condenser body is terminated by two right-angled portions 5 and 6. In known manner the portion 6 has four windows as shown in FIG. 2. The left hand side of the body 4 as seen in FIG. 1 terminates with a portion 7. The perforated plate 3 of each module is connected to a frame 8 by means of screws 9. Portions 10 and 11 are welded to appropriate faces of the frame to close the condenser body. The left hand water tank 12 on site is terminated by a plate 13 which is of the same shape as the part 6 shown in FIG. 2, which is why the part shown in FIG. 2 is referenced 13-6. The plate 13 is fixed to the four perforated plates 3 to hold them together.
Assembly thus takes place as follows: each module comprises a simple perforated plate 2 at its right hand end (as seen in FIG. 1) while at its left hand end it comprises the perforated plate 3 together with the parts 8, 10 and 11. The module made in this way is inserted from right to left through one of the four windows in the portion 6 until the perforated plate 2 abuts against the portion 6 via a gasket 18. The assembly is then fixed by means of screws 15 and the plates 11 are welded to the body 4. The water tank 12, 13 is then fixed on by means of screws 16.
Gaskets 14 and 19 are disposed on either side of the perforated plate 3, between the perforated plate and the frame 8 and between the perforated plate and the frame 13.
This structure has several drawbacks. In particular, it is impossible to verify the gaskets 18 and 19 once the parts are assembled and the weld 17 has been made; the welding 17 is done on site; the assembly is asymmetrical; and prior to assembly the modules are insufficiently rigid.
Preferred embodiments of the present invention mitigate these drawbacks and provide a solution which is more satisfactory, more practical, and more reliable.